Generally, a digital video signal having a plurality of gradations is expressed in such a manner that gradations of a single pixel are expressed in a plurality of bits. Thus, as a number of the gradations is increased, a sum of bit numbers, that is, a data amount is increased.
Therefore, the digital video signal is compressed in terms of bits so as to decrease the data amount, in case of high-speed serial transmission of data, or when it is necessary to have a smaller data amount to store data in a recording device as an image data.
However, in many cases apart from those special cases, a signal is transmitted in its original form and bit number as it is, without bit compression or data conversion. Particularly, in case of parallel transmission where a digital video signal, which is a signal having a plurality of bits and expresses information of each pixel, is divided per bit among a plurality of data transmission lines and transmitted per bit via the data transmission lines, a signal is, conventionally, transmitted in its original form and bit number, as it is.
However, in case of the parallel transmission in which a signal, contained in the digital video signal, having plural bits and expressing the information of each pixel is divided per bit among the plurality of the data transmission lines and transmitted per bit via the transmission lines, it is necessary to provide one data transmission line for 1 bit. Thus, if the signal is transmitted in its original form and bit number, it requires a great number of data transmission lines when bit number per pixel is large.
The digital video signal is usually composed of signals of three primary colors, namely: a red chrominance signal R, a green chrominance signal G, and blue chrominance signal B (hereinafter, just referred to as R, G, and B, respectively), whereas, in some cases, the digital video signal is composed of a luminance signal and two of color-difference signals. Each of the R, G and B is a gradation signal containing a plurality of bits. Therefore, for example, in case subjected to the parallel transmission between circuits is a digital video signal composed of R, G and B having 4 bits respectively, where the digital video signal is transmitted in its original form and bit number by being divided per bit among a plurality of transmission lines that are allotted for each bit, it is necessary to have twelve data transmission lines in total because one data transmission line is required for transmitting 1 bit.
As discussed above, in the conventional transmission method of the digital video signal, an increase in the bit number per pixel of the digital video signal leads to the increase in the number of the data transmission lines, at the same time.
Therefore, the conventional transmission method of the digital video signal requires a great number of data transmission lines on a substrate or in a circuit, in order to transmit the digital video signal on the substrate, or in the circuit. Such a problem is posed that this may demand a larger substrate or bigger circuit size. Another problem is that the increase in the number of the data transmission lines causes a greater consumption of power in a system (an image display apparatus) which is incorporated with a transmission apparatus and a reception apparatus, while increasing undesirable radiation noise generated by the data transmission lines.